The earth is a watery world with 71 percent of its surface covered by oceans and even its landmasses cut by rivers. The periodic rise and fall of all ocean waters is called tide, which results from gravitational attraction among the moon, sun, and earth. Although such gravitational attraction causes the vertical rise and fall of water, of particular interest to the renewable energy industry are the various horizontal or lateral movements commonly known as tidal currents or tidal streams from which great amounts of electricity can be produced. The advent of renewable energy, such as tidal energy, could be of vital importance to the future of civilization because reliance on fossil fuels cannot be sustained for another century. A transition toward renewable energy technologies would usher in a new age to supplant the age of fossil fuels, and address the problems of diminished oil reserves, destructive environmental impacts, and intractable religious conflicts.